Executive-frontal lobe cognitive dysfunction in schizophrenia: a symptom subtype analysis

Reduced temporal activation during a verbal fluency test in clinical high risk of psychosis: a functional near-infrared spectroscopy-based study

Background

Clinical high risk (CHR) of psychosis is a state in which positive symptoms cause the subjects distress but do not approach a severity level that fulfils the criteria for a psychotic episode. CHR exhibits cognitive deficits; however, the underlying neurobiological mechanisms remain unclear. This study aimed to investigate whether brain activation measured by the levels of oxygenated hemoglobin (oxy-Hb) in CHR subjects could be correlated with cognitive deficits.

Methods

Fifty-eight CHR individuals who fulfilled the criteria for attenuated positive syndrome as specified in the Structured Interview for Prodromal Syndrome (SIPS) and the Scale of Prodromal Syndrome (SOPS) and 58 age- and sex-matched healthy participants were included in the study. All subjects completed the Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) Consensus Cognitive Battery (MCCB) that includes tests measuring attention, verbal memory, verbal fluency, executive function, and general intelligence. Functional near-infrared spectroscopy (fNIRS) was used to measure the level of oxy-Hb in the dorsolateral prefrontal and frontotemporal cortices.

Results

We observed significantly decreased oxy-Hb levels in channel 32 (located in the right superior temporal gyrus, rSTG)) within the CHR individuals compared with that in the healthy controls (HCs) (t=−3.44, Bonferroni-corrected p=0.002), indicating lower brain activity. A significant positive correlation was observed between task-related β values and working memory in the CHR group (r=0.35, p=0.008).

Conclusions

The brain activation of rSTG is abnormal among subjects at clinicial high risk for psychosis. This abnormality is probably associated with the neural mechanisms of deficits in the working memory during the early stage of psychosis.

No influence of sex on the relationship between schizotypy factors and executive control across the schizophrenia spectrum

Sex differences in symptoms and executive control across schizophrenia spectrum disorders (SSD) are consistently reported. Similarly, these findings of sex differences are also observed in schizotypy, that is, schizophrenia-like features occurring in healthy individuals in the absence of a clinical diagnosis. This study aimed to examine the relationships between performance on three major domains of executive control: performance monitoring, response inhibition, and cognitive set-shifting, and schizotypy factor scores in both SSD patients and healthy controls (HCs), and whether sex moderated any relationships observed. A total of 111 (67 males and 44 females) patients with SSD and 258 (129 males and 129 females) HCs were included in this study. Schizotypal personality traits (in both SSD and HC) was assessed using the Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE). Executive control performance was assessed using seven tasks. Stepwise linear regressions revealed that performance on cognitive set-shifting tasks was significantly associated with the introvertive anhedonia, cognitive disorganisation, and unusual experiences subscales of the O-LIFE. When sex was examined as a moderator, it was not a significant moderator of any of the relationships between cognitive set-shifting tasks and schizotypy factors. The results suggest that independent of sex, cognitive set-shifting ability is associated to an increased vulnerability to schizotypal personality traits, although performance monitoring and response inhibition did not.

Dissociative Effects of Neuropeptide S Receptor Deficiency and Nasal Neuropeptide S Administration on T-Maze Discrimination and Reversal Learning

Cognitive flexibility refers to the ability to modify learned behavior in response to changes in the environment. In laboratory rodents, cognitive flexibility can be assessed in reversal learning, i.e., the change of contingencies, for example in T-maze discrimination learning. The present study investigated the role of the neuropeptide S (NPS) system in cognitive flexibility. In the first experiment, mice deficient of NPS receptors (NPSR) were tested in T-maze discrimination and reversal learning. In the second experiment, C57BL/6J mice were tested in the T-maze after nasal administration of NPS. Finally, the effect of nasal NPS on locomotor activity was evaluated. NPSR deficiency positively affected the acquisition of T-maze discrimination but had no effects on reversal learning. Nasal NPS administration facilitated reversal learning and supported an allocentric learning strategy without affecting acquisition of the task or locomotor activity. Taken together, the present data show that the NPS system is able to modulate both acquisition of T-maze discrimination and its reversal learning. However, NPSR deficiency only improved discrimination learning, while nasal NPS administration only improved reversal learning, i.e., cognitive flexibility. These effects, which at first glance appear to be contradictory, could be due to the different roles of the NPS system in the brain regions that are important for learning and cognitive flexibility.

In schizophrenia, psychomotor retardation is associated with executive and memory impairments, negative and psychotic symptoms, neurotoxic immune products and lower natural IgM to malondialdehyde

Objectives: Stable-phase schizophrenia comprises two distinct entities namely Major Neuro-Cognitive Psychosis (MNP) and simple NP (SNP), which are defined by neuroimmune and neurocognitive abnormalities.Methods: This study investigates associations of psychomotor retardation (PMR), clinical and biomarker characteristics of schizophrenia. We recruited 40 healthy controls and 79 schizophrenia patients and measured IgA responses to tryptophan catabolites (TRYCATs), IgM to malondialdehyde and nitroso (NO)-cysteinyl, CCL-11, an immune activation index based on cytokine levels, and motor screening task (MOT) scores.Results: PMR differentiated schizophrenia from controls and MNP from SNP. In addition, PMR was strongly associated with impairments in executive functions and episodic and semantic memory, psychotic, hostility, excitation, mannerism and negative (PHEMN) symptoms. Around 50% of the variance in PMR was predicted by the cumulative effects of the immune activation index, CCL-11, TRYCATs, NO-Cysteinyl and natural IgM. PRM can reliably be combined with PHEMN symptoms, memory and executive impairments into one latent vector reflecting overall severity of schizophrenia.Conclusions: PMR is a key psychopathological feature of schizophrenia mainly MNP. In addition, PMR may be driven by deficits in the compensatory immune-regulatory system and increased production of neurotoxic immune products, namely TRYCATs, IgM to NO-cysteinyl, and CCL-11, an endogenous cognition deteriorating chemokine.

Motivational deficits in schizophrenia relate to abnormalities in cortical learning rate signals

Individuals from across the psychosis spectrum display impairments in reinforcement learning. In some individuals, these deficits may result from aberrations in reward prediction error (RPE) signaling, conveyed by dopaminergic projections to the ventral striatum (VS). However, there is mounting evidence that VS RPE signals are relatively intact in medicated people with schizophrenia (PSZ). We hypothesized that, in PSZ, reinforcement learning deficits often are not related to RPE signaling per se but rather their impact on learning and behavior (i.e., learning rate modulation), due to dysfunction in anterior cingulate and dorsomedial prefrontal cortex (dmPFC). Twenty-six PSZ and 23 healthy volunteers completed a probabilistic reinforcement learning paradigm with occasional, sudden, shifts in contingencies. Using computational modeling, we found evidence of an impairment in trial-wise learning rate modulation (α) in PSZ before and after a reinforcement contingency shift, expressed most in PSZ with more severe motivational deficits. In a subsample of 22 PSZ and 22 healthy volunteers, we found little evidence for between-group differences in VS RPE and dmPFC learning rate signals, as measured with fMRI. However, a follow-up psychophysiological interaction analysis revealed decreased dmPFC-VS connectivity concurrent with learning rate modulation, most prominently in individuals with the most severe motivational deficits. These findings point to an impairment in learning rate modulation in PSZ, leading to a reduced ability to adjust task behavior in response to unexpected outcomes. At the level of the brain, learning rate modulation deficits may be associated with decreased involvement of the dmPFC within a greater RL network.

Variation in fourteen brain structure volumes in schizophrenia: A comprehensive meta-analysis of 246 studies

Despite hundreds of structural MRI studies documenting smaller brain volumes on average in schizophrenia compared to controls, little attention has been paid to group differences in the variability of brain volumes. Examination of variability may help interpret mean group differences in brain volumes and aid in better understanding the heterogeneity of schizophrenia. Variability in 246 MRI studies was meta-analyzed for 13 structures that have shown medium to large mean effect sizes (Cohen's d≥0.4): intracranial volume, total brain volume, lateral ventricles, third ventricle, total gray matter, frontal gray matter, prefrontal gray matter, temporal gray matter, superior temporal gyrus gray matter, planum temporale, hippocampus, fusiform gyrus, insula; and a control structure, caudate nucleus. No significant differences in variability in cortical/subcortical volumes were detected in schizophrenia relative to controls. In contrast, increased variability was found in schizophrenia compared to controls for intracranial and especially lateral and third ventricle volumes. These findings highlight the need for more attention to ventricles and detailed analyses of brain volume distributions to better elucidate the pathophysiology of schizophrenia.

The association between cognitive deficits and prefrontal hemodynamic responses during performance of working memory task in patients with schizophrenia

Schizophrenia-associated cognitive deficits are resistant to treatment and thus pose a lifelong burden. The Brief Assessment of Cognition in Schizophrenia (BACS) provides reliable and valid assessments across cognitive domains. However, because the prefrontal functional abnormalities specifically associated with the level of cognitive deficits in schizophrenia have not been examined, we explored this relationship. Patients with schizophrenia (N=87) and matched healthy controls (N=50) participated in the study. Using near-infrared spectroscopy (NIRS), we measured the hemodynamic responses in the prefrontal and superior temporal cortical surface areas during a working memory task. Correlation analyses revealed a relationship between the hemodynamics and the BACS composite and domain scores. Hemodynamic responses of the left dorsolateral prefrontal cortex (DLPFC) and left frontopolar cortex (FPC) in the higher-level-of-cognitive-function schizophrenia group were weaker than the responses of the controls but similar to those of the lower-level-of-cognitive-function schizophrenia group. However, hemodynamic responses in the right DLPFC, bilateral ventrolateral PFC (VLPFC), and right temporal regions decreased with increasing cognitive deficits. In addition, the hemodynamic response correlated positively with the level of cognitive function (BACS composite scores) in the right DLPFC, bilateral VLPFC, right FPC, and bilateral temporal regions in schizophrenia. The correlation was driven by all BACS domains. Our results suggest that the linked functional deficits in the right DLPFC, bilateral VLPFC, right FPC, and bilateral temporal regions may be related to BACS-measured cognitive impairments in schizophrenia and show that linking the neurocognitive deficits and brain abnormalities can increase our understanding of schizophrenia pathophysiology.

Preserved Learning during the Symbol-Digit Substitution Test in Patients with Schizophrenia, Age-Matched Controls, and Elderly

OBJECTIVE

Speed of processing, one of the main cognitive deficits in schizophrenia is most frequently measured with a digit-symbol-coding test. Performance on this test is additionally affected by writing speed and the rate at which symbol-digit relationships are learned, two factors that may be impaired in schizophrenia. This study aims to investigate the effects of sensorimotor speed, short-term learning, and long-term learning on task performance in schizophrenia. In addition, the study aims to explore differences in learning effects between patients with schizophrenia and elderly individuals.

METHODS

Patients with schizophrenia (N = 30) were compared with age-matched healthy controls (N = 30) and healthy elderly volunteers (N = 30) during the Symbol-Digit Substitution Test (SDST). The task was administered on a digitizing tablet, allowing precise measurements of the time taken to write each digit (writing time) and the time to decode symbols into their corresponding digits (matching time). The SDST was administered on three separate days (day 1, day 2, day 7). Symbol-digit repetitions during the task represented short-term learning and repeating the task on different days represented long-term learning.

RESULTS

The repetition of the same symbol-digit combinations within one test and the repetition of the test over days resulted in significant decreases in matching time. Interestingly, these short-term and long-term learning effects were about equal among the three groups. Individual participants showed a large variation in the rate of short-term learning. In general, patients with schizophrenia had the longest matching time whereas the elderly had the longest writing time. Writing time remained the same over repeated testing.

CONCLUSION

The rate of learning and sensorimotor speed was found to have a substantial influence on the SDST score. However, a large individual variation in learning rate should be taken into account in the interpretation of task scores for processing speed. Equal learning rates among the three groups suggest that unintentional learning in schizophrenia and in the elderly is preserved. These findings are important for the design of rehabilitation programs for schizophrenia.

Executive functioning in schizophrenia: the result of impairments in lower order cognitive skills?

Executive functioning (EF) impairments are common in schizophrenia. There are two propositions regarding the causes of these impairments: (1) executive impairments are the result of the compounding effects of deficits in lower order cognitive skills (e.g. processing speed, attention) or (2) EF impairments exist in their own right regardless of lower order skills. It is difficult to examine the separable effects of lower order cognitive skills on EF given the overlap required to complete most neuropsychological measures. One battery designed to parcel out the contributions of lower order skills from EF is the Delis-Kaplan Executive Function System (D-KEFS). Inhibition and switching specifically were examined using the D-KEFS versions of the Stroop and Trails task. No group differences in task performance after controlling for lower level skills would provide evidence for a generalised cognitive deficit. Group differences remaining after controlling for these influences would suggest a disproportionate deficit. Results supported both propositions. On both tasks, group differences reflecting slowed reaction time in the schizophrenia group disappeared when lower order skills were controlled for. Differences between groups performance in errors were only evident on the most complex versions of each task with more errors made by the schizophrenia group. These results suggest that (1) both RT and error data are needed to provide a full picture of performance and (2) the relationship between lower order and EF is too complex to provide support for one or the other proposal.

Distinct episodic verbal memory profiles in schizophrenia

According to some authors, episodic memory impairment may be a feature shared by all schizophrenic patients, whereas others argue in favor of the mnesic heterogeneity. Our aims were to determine whether patients can be grouped based on according to their mnesic performances. The California Verbal Learning Test (CVLT), an episodic verbal learning test, was compared in 61 schizophrenic patients and 61 matched healthy subjects. The 32 indices were calculated using CVLT Scoring Software. This process allowed us to describe patients' episodic processes in detail (encoding, storage, retrieval). We isolated one group with normative data, another showed impairment of both encoding and retrieval processes, and in the last one, only encoding process was impaired. As schizophrenia is heterogeneous with regard to episodic memory, impairments should not be considered as a common core to the various forms of the illness and it would be fruitful to systematically assess episodic processes in detail to take into account individual abilities and challenges.

No correlation between plasma NMDA-related glutamatergic amino acid levels and cognitive function in medicated patients with schizophrenia

OBJECTIVE

Disrupted glutamatergic neurotransmission and cognitive functions are key components in the pathophysiology of schizophrenia. Changes in levels of serum/plasma glutamatergic amino acids, such as glutamate, glycine, and L- and D-serine may be possible clinical markers. Following our recent findings that peripheral blood levels of endogenous glycine, alanine, and especially D-serine may reflect the degree/change in symptoms in schizophrenia, here we investigated whether these plasma amino acid levels may also reflect the status of cognitive functions in schizophrenia.

METHODS

One hundred eight Japanese patients with schizophrenia were evaluated with cognitive assessment batteries at the time that plasma glutamatergic amino acid levels were measured using high-performance liquid chromatography. For analyzing cognitive functions, batteries for reflection prefrontal cortex cognitive functions, verbal fluency tests, the Stroop test, and the digit span forward and backward tests were administered.

RESULTS

Results failed to show a relationship between any plasma glutamatergic amino acid level and cognitive batteries.

CONCLUSIONS

Our results suggest that plasma glutamatergic amino acid levels may be significant biological markers that reflect the condition or a dramatic change at the time of testing, especially in severely affected patients, but they do not reflect cognitive function.

Dimensions of executive functioning in schizophrenia and their relationship with processing speed

CONTEXT

The nature of executive dysfunction in schizophrenia is nebulous, due to inconsistencies in conceptualizing and operationalizing the construct, and the broader question of whether schizophrenia is best characterized in terms of specific vs generalized cognitive deficits. The current study aimed to determine whether executive functions represent unitary vs diverse constructs in schizophrenia.

METHODS

Participants included 145 community-dwelling individuals with schizophrenia. Executive functions were measured with the Delis-Kaplan Executive Functioning System (D-KEFS). We conducted an exploratory factor analysis (EFA) with principal axis factoring, as well as parallel analyses to examine the latent constructs underlying the D-KEFS tasks, a second EFA on weighted residuals of the D-KEFS tasks (after accounting for processing speed measured with the Digit Symbol task), and bivariate correlations to examine relationships between the D-KEFS components and relevant demographic and clinical variables, crystallized verbal knowledge, and functional capacity.

RESULTS

EFA of the D-KEFS tasks yielded 2 factors (cognitive flexibility/timed tests and abstraction). EFA of the processing speed-weighted D-KEFS residuals also yielded 2 factors (cognitive flexibility and abstraction). Cognitive flexibility was negatively correlated with psychopathology. Better abstraction was associated with higher education, shorter illness duration, and better functional capacity. Both factors were positively correlated with crystallized verbal knowledge.

CONCLUSIONS

Executive functions in schizophrenia could be parsed into 2 partially related but separable subconstructs. Future efforts to elucidate functional outcomes as well as neurobiological underpinnings of schizophrenia may be facilitated by attending to the distinction between cognitive flexibility and abstraction.

A proton magnetic resonance spectroscopy study in schizoaffective disorder: comparison of bipolar disorder and schizophrenia

The aim of this study was to compare schizoaffective disorder, bipolar disorder and schizophrenia based on (1)H-MRS metabolite values in dorsolateral prefrontal cortex and executive functions. The subjects comprised 15 patients with bipolar disorder type I (BD), 15 with schizophrenia (SCH), 15 with schizoaffective disorder (SAD) and 15 healthy controls. We performed proton magnetic resonance spectroscopy ((1)H-MRS) of the dorsolateral prefrontal cortex (DLPFC) bilaterally. Levels of N-acetyl aspartate (NAA), choline-containing compounds (Cho) and creatine-containing compounds (Cr) were measured in the DLPFC using (1)H-MRS. We administered the Wisconsin Card Sorting Test (WCST) and the Stroop Test (ST) to evaluate executive functions. The SAD, BD and SCH patients had lower levels of NAA than the control group. The SAD and BD patients had low levels of Cho compared to the control group. The left DLPFC Cr levels in all of the patient groups and the right DLPFC Cr levels in the BD and SAD groups were lower than in the control group. The levels of NAA Cho and Cr were not related to executive functions and attention performance. Cr level were related to attention processes, only in SCH. Our results indicate that NAA levels are reduced in schizoaffective disorder, bipolar disorder and schizophrenia, but the reduction in the levels of NAA is not a distinctive feature among these three illnesses. Schizoaffective and bipolar disorders have similar features related to the levels of compounds containing Cho and Cr. This similarity may be related to these illnesses both having an affective basis.

Effect of blonanserin on cognitive function in antipsychotic-naïve first-episode schizophrenia

OBJECTIVE

The purpose of this study was to evaluate the effects of blonanserin, a novel antipsychotic, on cognitive function in first-episode schizophrenia.

METHODS

Twenty-four antipsychotic-naïve patients with first-episode schizophrenia participated in the study. Blonanserin was given in an open-label design for 8 weeks. The Brief Assessment of Cognition in Schizophrenia-Japanese language version (BACS-J) was administered as the primary outcome measure at baseline and 8 weeks. Clinical evaluation included the Positive and Negative Syndrome Scale (PANSS), the Schizophrenia Quality of Life Scale-Japanese language version (SQLS-J), and the Clinical Global Impression-Severity of Illness Scale (CGI-S). To exclude the possibility of retest effects on the BACS-J, 10 age-matched patients with chronic schizophrenia treated with blonanserin were tested at baseline and after an 8-week interval.

RESULTS

Twenty first-episode patients completed the study. Repeated measures analysis of covariance revealed a significant group-by-time interaction effect on the letter fluency task due to better performance in the first-episode group, but not in the control group. Main effect of time or group-by-time interaction effect on the Tower of London task was not significant; however, the first-episode group, but not the control group, showed substantial improvement with a moderate effect size. All items on the PANSS, SQLS-J, and CGI-S significantly improved after 8 weeks of treatment.

CONCLUSIONS

These results suggest that blonanserin improves some types of cognitive function associated with prefrontal cortical function.

Patient subgroups of schizophrenia based on the Positive and Negative Syndrome Scale: composition and transition between acute and subsided disease states

The present study focuses on schizophrenia patient subgroups with specific symptom pattern using the Positive and Negative Syndrome Scale (PANSS). In this report, we intend to (1) provide a more appropriate analytic method for exploring the subgroups based on PANSS data, (2) validate identified subgroups with external variables, and (3) estimate probabilities of subgroup changes between 2 disease states. The analyzed data include 219 acute-state patients who had completed the PANSS within 1 week of index admission and 225 subsided-state patients who were living in the community and under family care. Regression extension of latent class analysis was performed. We found that acute schizophrenia can be classified into 4 subgroups--whole syndrome, whole syndrome without hostility, partial syndrome with negative symptoms, and partial syndrome with pure reality distortion--and that subsided schizophrenia can be classified into 3 subgroups--florid symptom, marked negative, and remitted. Patients of the whole syndrome, whole syndrome without hostility, partial syndrome with negative symptoms, and partial syndrome with pure reality distortion subgroups at the acute state were most likely to transit to the florid symptom (61%), florid symptom (48%), marked negative (42%), and remitted (56%) subgroups at the subsided state, respectively. Significant relationships of obtained subgroups with sociodemographic variables and neurocognitive variables were identified. These results of different subgroups will provide the background for facilitating current molecular, genetic, and neurobiological studies of schizophrenia.

Effects of acamprosate on cognition in a treatment study of patients with schizophrenia spectrum disorders and comorbid alcohol dependence

Problems with memory and attention are common to both schizophrenia and alcohol dependence. The objectives of this study were to examine the effect of acamprosate treatment on cognition and to assess whether the changes in drinking patterns or psychotic symptoms were related to changes in cognitive functioning. Outpatients with schizophrenia spectrum disorders and alcohol dependence (n = 23) were randomized (double-blind) to either acamprosate or placebo treatment for 12 weeks. Assessments (baseline and week 12) included alcohol use, symptoms of psychosis, memory, and attention. The results showed that acamprosate had no effect on cognitive functioning and that there was no relationship between change in alcohol consumption or psychotic symptoms and change in cognitive functioning in this sample of patients. The finding that acamprosate had no negative effects on cognition is clinically relevant and reinforces previous reports that acamprosate can be used safely for alcohol reduction in this group of patients.

A cognitive regulatory control model of schizophrenia

A puzzling aspect of schizophrenia concerns the relationship between negative and positive symptoms. Perspectives suggesting that they arise from the same pathophysiological process are not consistent with the numerous differences such as treatment response, and the underlying neurochemistry relevant to treatment. Explanations viewing negative and positive symptoms as independent processes or diseases cannot readily account for the typical developmental course of schizophrenia, consisting of a lengthy prodromal phase of negative followed by positive symptoms. A model of schizophrenia is presented positing that negative and positive symptoms are distinct but interrelated processes, with the former bringing forth the latter due to damaged or impaired cognitive regulatory control processes. The extensive cognitive distortions, thought form variants, and sensory perceptual experiences comprising psychosis represent a natural propensity derived from the evolution of human intelligence. To facilitate reality congruency typically necessary for adaptive functioning, cognitive regulatory control processes normally prevent these extreme variants from entering the conscious and awake state. During sleep when there is no need for reality congruency the cognitive regulatory control processes are deactivated and psychotic equivalents are expressed. Psychological defensive functioning can also deactivate these processes and allow psychosis to manifest. The negative symptoms of schizophrenia are seen as arising from diverse neural deficits that impair to varying degrees the cognitive regulatory control processes, thus producing psychosis. The pattern of neural damage determines the negative symptom profile, and the impact on cognitive regulatory control processes influences whether negative or positive symptoms dominate or exist in relatively equal proportions.

The relationships between schizophrenia symptom dimensions and executive functioning components

Research investigating the relationships between executive functioning impairments and the positive, negative, and cognitive schizophrenia symptoms has produced inconsistent results. This inconsistency may be due to the tendency to view executive functioning as a unified process as opposed to multiple fractionated processes. A fractionated model of executive functioning has been supported in several studies of various populations, but few schizophrenia studies have used the factor analytic methods of these studies to empirically determine separate executive functioning components, causing conclusions regarding the relationships between these components and schizophrenia symptoms to be unreliable. The purposes of the present study were to (1) identify separate components of executive functioning by conducting a factor analysis of the performance of individuals with schizophrenia on the Delis Kaplan Executive Function System (D-KEFS) and (2) investigate the relationships between executive functioning components and the three schizophrenia symptom dimensions by correlating the derived factor scores with the scale scores of the Positive and Negative Symptom Scale (PANSS). An exploratory factor analysis revealed two separate components: inhibition/set shifting and mental flexibility. The results showed that the symptom dimensions were differentially related to impairments in executive functioning, with both negative and cognitive symptoms associated with the inhibition/set shifting component, cognitive symptoms alone associated with the mental flexibility component, and positive symptoms unrelated to either component.

Deconstructing processing speed deficits in schizophrenia: application of a parametric digit symbol coding test

Cognitive processing inefficiency, often measured using digit symbol coding tasks, is a putative vulnerability marker for schizophrenia and a reliable indicator of illness severity and functional outcome. Indeed, performance on the digit symbol coding task may be the most severe neuropsychological deficit patients with schizophrenia display at the group level. Yet, little is known about the contributions of simpler cognitive processes to coding performance in schizophrenia (e.g. decision making, visual scanning, relational memory, motor ability). We developed an experimental behavioral task, based on a computerized digit symbol coding task, which allows the manipulation of demands placed on visual scanning efficiency and relational memory while holding decisional and motor requirements constant. Although patients (n=85) were impaired on all aspects of the task when compared to demographically matched healthy comparison subjects (n=30), they showed a particularly striking failure to benefit from the presence of predictable target information. These findings are consistent with predicted impairments in cognitive processing speed due to schizophrenia patients' well-known memory impairment, suggesting that this mnemonic deficit may have consequences for critical aspects of information processing that are traditionally considered quite separate from the memory domain. Future investigation into the mechanisms underlying the wide-ranging consequences of mnemonic deficits in schizophrenia should provide additional insight.

Working memory in schizophrenia: a meta-analysis

BACKGROUND

Memory impairment is being recognized increasingly as an important feature of the neuropsychology of schizophrenia. Dysfunction of working memory, a system for the short-term storage and manipulation of information, may relate to a number of core symptoms of schizophrenia. Many studies have examined working memory function in schizophrenia but a clear understanding of the nature and extent of any deficit has been elusive.

METHOD

A systematic review and meta-analysis of studies comparing working memory function in subjects with schizophrenia and healthy controls was performed. Following a comprehensive literature search, meta-analyses were conducted on 36 measures of phonological, visuospatial and central executive working memory functioning, encompassing 441 separate results from 187 different studies.

RESULTS

Statistically significant effect sizes were found for all working memory measures, indicating deficits in schizophrenia groups. Some of these were robust findings in the absence of evidence of significant heterogeneity or publication bias. Meta-regression analyses showed that the working memory deficit was not simply explained by discrepancies in current IQ between schizophrenia and control groups.

CONCLUSIONS

Large deficits in working memory were demonstrated in schizophrenia groups across all three working memory domains. There were, however, no clear differences across subdomains or between particular working memory tasks. There was substantial heterogeneity across results that could only be partly explained.

Does the ability to sustain attention underlie symptom severity in schizophrenia?

An association between deficits in executive control, particularly inhibitory control, and more severe negative and disorganised symptoms of schizophrenia has been widely reported. The importance of more basic aspects of attention, often referred to as 'vigilant' or 'sustained' attention, to this relationship remains unclear. This study examined the contribution of sustained attention to symptom severity using the Sustained Attention to Response Task (SART) in 69 patients with schizophrenia. We found that negative and disorganised symptom severity scores were correlated with sustained attention, working memory, and psychomotor speed. The ability to sustain attention significantly predicted variance in negative symptom severity but not disorganised symptoms, which were instead predicted by working memory performance. These data suggest that this component of attention at least partly explains variance in negative symptoms.

A neurocognitive model of borderline personality disorder: effects of childhood sexual abuse and relationship to adult social attachment disturbance

Borderline personality disorder (BPD) is a paradigmatic disorder of adult attachment, with high rates of antecedent childhood maltreatment. The neurocognitive correlates of both attachment disturbance and maltreatment are both presently unknown in BPD. This study evaluated whether dimensional adult attachment disturbance in BPD is related to specific neurocognitive deficits, and whether childhood maltreatment is related to these dysfunctions. An outpatient BPD group (n=43) performed nearly 1 SD below a control group (n=26) on short-term recall, executive, and intelligence functions. These deficits were not affected by emotionally charged stimuli. In the BPD group, impaired recall was related to attachment-anxiety, whereas executive dysfunction was related to attachment-avoidance. Abuse history was correlated significantly with executive dysfunction and at a trend level with impaired recall. Neurocognitive deficits and abuse history exhibited both independent and interactive effects on adult attachment disturbance. These results suggest that (a) BPD patients' reactivity in attachment relationships is related to temporal-limbic dysfunction, irrespective of the emotional content of stimuli, (b) BPD patients' avoidance within attachment relationships may be a relational strategy to compensate for the emotional consequences of frontal-executive dysregulation, and (c) childhood abuse may contribute to these neurocognitive deficits but may also exert effects on adult attachment disturbance that is both independent and interacting with neurocognitive dysfunction.

Less unique variance than meets the eye: overlap among traditional neuropsychological dimensions in schizophrenia

The magnitude of the overlap among dimensions of neuropsychological test performance in schizophrenia has been the subject of perennial controversy. This issue has taken on renewed importance with the recent focus on cognition as a treatment target in schizophrenia. A substantial body of factor analytic literature indicates that dimensions are separable in schizophrenia. However, this literature is generally uninformative as to whether the separable dimensions are independent, weakly correlated, or strongly correlated. Factor analyses have often used methods (ie, principal components analysis with orthogonal rotation) that preclude this determination, and correlations among factor-based domain composites and underlying measures have been reported infrequently in these studies. Current meta-analyses of reported "between-dimension" correlations for individual neuropsychological measures and for cognitive domain composite variables indicate that cognition variables in schizophrenia are correlated, on average, at a "medium" level of r = 0.37 for individual measures from different cognitive dimensions and r = 0.45 for domain composites. Because these are mean bivariate correlations, the multiple correlation of an individual measure with all the other measures in a cognitive battery is likely to be higher. Measure reliabilities of 0.80 or less also imply greater commonality among traditional neuropsychological measures. In short, there are underappreciated constraints on the amount of reliable cognitive performance variance in traditional neuropsychological test batteries that is free to vary independently. The ability of such batteries to reveal cognitive domain-specific treatment effects in schizophrenia may be much more limited than is generally assumed.

Auditory Oddball fMRI in Schizophrenia: Association of Negative Symptoms with Regional Hypoactivation to Novel Distractors

Schizophrenia is associated with abnormal processing of salient stimuli, which may contribute to clinical symptoms. We used fMRI and a standard auditory 3-stimulus task to examine attention processing. Target stimuli and novel distractors were presented to 17 patients and 21 healthy controls and activation was correlated with negative and positive symptoms. To targets, patients overactivated multiple regions including premotor cortex, anterior cingulate, temporal cortex, insula, and hippocampus, and also showed attenuated deactivation within occipital cortex. To distractors, patients overactivated left ventrolateral prefrontal cortex. This overactivation may reflect hypersensitivity to salient stimuli in schizophrenia. Patients also exhibited an inverse correlation between negative symptom severity and activation to novel distractors in the dorsolateral prefrontal cortex, premotor area, and ventral striatum. Novelty-induced activity within prefrontal cortex and ventral striatum may represent a useful intermediate phenotype for studies of negative symptoms.

Nitric oxide synthase inhibition attenuates phencyclidine-induced disruption of cognitive flexibility

Schizophrenia encompasses, amongst other symptoms, a heavy load of cognitive dysfunctionality. Using the psychotomimetic agent, phencyclidine (PCP), we have previously found that PCP-induced disruptions of cognitive function in translational rodent models of schizophrenia are dependent on nitric oxide (NO) production. In the present study, male Sprague-Dawley rats were subjected to a Morris water maze task designed to assess cognitive flexibility (i.e. the ability to cope with an increasingly demanding cognitive task) by means of a "constant reversal learning paradigm". Experiments were conducted to evaluate the effects of the NO synthase inhibitor, L-NAME (10 mg/kg), on PCP-induced (2 mg/kg) impairments. Control animals significantly improved their learning over the first 3 consecutive days, whereas PCP-treated animals failed to show any significant learning. Pretreatment with L-NAME normalized the PCP-induced disruption of learning to control levels. These findings suggest that PCP-induced disruptions of cognitive flexibility (i.e. ability to modify behaviour according to an increasingly demanding cognitive task) are dependent upon NO production. These observations, together with accumulated clinical findings, suggest that the NO system is a potential treatment target for cognitive dysfunctions in schizophrenia.

Executive function in schizophrenia: what impact do antipsychotics have?

Cognitive dysfunction is a major component of schizophrenia, with deficits in executive function particularly pertinent to successful daily living and outcome. Executive deficits and negative/disorganised symptoms remain relatively resistant to amelioration by antipsychotic medication in comparison to positive symptoms. While there is a relative paucity of data on the effects of antipsychotics on specific executive deficits, atypical antipsychotics would appear to be more beneficial than typical antipsychotics at improving these functions, with muscarinic, glutamatergic and cholinergic systems variously implicated. Recent research focusing on the relationships between specific symptoms and specific executive deficits holds important implications for future psychopharmacological interventions in the area by elucidating the neural substrates and pathways which underpin schizophrenic symptomatology. This review attempts to evaluate the research thus far for the specific executive components of spatial working memory (SWM), inhibition, sustained attention and set shifting. Issues significant to future psychopharmacology in the area are discussed, with particular emphasis on the need for a greater consensus in methodology and definition executive function research in schizophrenia.

Context processing and negative symptoms in schizophrenia

The objective of the study was to test the assumption that patients with a high level of negative symptoms show disproportionate impairments of inhibition and multitasking, both representing an underlying context processing mechanism. A total of 26 schizophrenia patients scoring high or low on negative symptoms (Positive and Negative Syndrome Scale) and a group of 13 healthy controls were assessed on measures of response inhibition (AX- Continuous Performance Task, Stroop Test) and multitasking (Dual Task, Trail Making Test). Only the high negative symptoms group showed significantly higher inhibition costs and multitasking costs than healthy controls. In the AX-Continuous Performance Test, inhibition costs exceeded context costs in patients with more severe negative symptoms, while in controls a tendency towards the reverse pattern emerged. There were no statistically significant effects involving the patient group with lower negative symptom scores. The pattern of results suggests that primarily patients with more severe negative symptoms have difficulties benefiting from contextual information. The deficit may manifest itself via increased multitasking costs and increased inhibition costs but also via reduced context costs.

Creative thinking in schizophrenia: the role of executive dysfunction and symptom severity

INTRODUCTION

This study examines the notion of enhanced creative thinking in schizophrenia and determines the mediating role of executive dysfunction and symptom severity in this relationship.

METHOD

Patients with chronic schizophrenia (n=28) were assessed on varied facets of creative cognition and standard tests of executive control relative to matched healthy control participants (n=18).

RESULTS

Multivariate analyses revealed poorer performance by the patient group across almost all creative and executive function measures, except in the ability to be unconstrained by the influence of restrictive examples. Symptom-based contrasts using partial correlations revealed that differences were most extensive in the presence of thought disorder. Using hierarchical regression analyses, performance on the executive function tasks was found to play a mediatory role on specific aspects of creative cognition.

CONCLUSIONS

Results are at odds with the popular notion of enhanced creative thinking in schizophrenia, but elucidate complex interactions between executive control and certain facets of creative thinking. In particular, performance of the schizophrenia group on measures that tap creativity elements of fluency and relevance were either partially or fully mediated by their performance on the executive control tasks, but this was not true of measures of originality.

Subclinical psychotic experiences and cognitive functioning as a bivariate phenotype for genetic studies in the general population

OBJECTIVE

Cognitive deficits may be vulnerability markers for the development of schizophrenia. This study examined whether cognitive deficits are related to specific dimensions of subclinical psychotic experiences and whether associations between these variables are caused by additive genetic, common environmental and/or individual-specific environmental factors.

METHOD

A general population sample of 298 female twin pairs completed the Community Assessment of Psychic Experiences and a neuropsychological test battery. Associations between subclinical positive and negative psychotic dimensions and neuropsychological factors (episodic memory and information processing speed) were examined. Univariate correlation and structural equation analyses were performed to explore the role of genetic and environmental factors in the phenotypes separately. Bivariate correlation and structural equation analyses were applied to examine the causes of association.

RESULTS

There were significant correlations between information processing speed and both the positive (r=.11; p<.05) and the negative dimension (r=.10; p<.05). For the negative dimension and for speed of processing, the data suggested a model that included genetic factors. The observed phenotypic correlation between the negative dimension and information processing speed could be solely explained in terms of additive genetic factors. Although the comparison of the correlations for MZ and DZ pairs did not give a clear indication as to the underlying causes of the association, structural equation modelling suggested that the observed phenotypic correlation between the negative dimension and information processing speed could be solely explained in terms of additive genetic factors.

CONCLUSION

Negative symptoms and information processing speed are associated at the subclinical level and this association appears to be influenced by genetic factors exclusively. Bivariate psychosis phenotypes may represent suitable candidates for molecular genetic studies in the general population.

The frontal hypothesis of cognitive aging: factor structure and age effects on four frontal tests among healthy individuals

With 101 healthy aging adult participants, the authors investigated whether executive functions are a unitary concept. The authors established the factor structure of the Wisconsin Card Sorting Test (WCST; E. A. Berg, 1948), the Stroop color and word test (C. J. Golden, 1978), verbal fluency using the Controlled Oral Word Association Test (COWAT; Benton, 1967), and the Digits Backwards subtest of the Wechsler Adult Intelligence Scale-Revised (WAIS-R; D. Wechsler, 1981). The authors also evaluated the extent to which age and other demographic variables predicted common underlying properties of these frontal tests. Results revealed an age-related decline in executive abilities differentially reflected by the selected tasks. These data suggest caution using the COWAT to evaluate executive abilities in older people. The authors interpret findings to support the unitary view of executive abilities and the executive decline proposed by the frontal hypothesis.

Intrusion errors in explicit memory: their differential relationship with clinical and social outcome in chronic schizophrenia

INTRODUCTION

Memory deficits might account for clinical and adaptive differences between groups of patients with chronic schizophrenia. We investigated the qualitative factors of memory that influence clinical and social status.

METHODS

Psychosocial functioning, clinical symptoms, and memory function were assessed in 99 patients at four time points over a 16-month period using recall scores for semantically related words, unrelated words, paired associated learning, and word span. An initial cluster analysis using symptom assessment data from all four time points divided the sample into three groups: patients with low symptoms ratings that remained stable throughout the study period (low symptom-stable group - LSSG; N=51); patients with initially high symptoms ratings that subsequently improved (high symptom-improved group - HSIG; N=32); and patients with initially high symptoms ratings that deteriorated during the follow-up (high symptom-deteriorated group - HSDG; N=16).

RESULTS

Memory was better preserved in LSSG compared to HSIG and HSDG patients. Recall performance was generally better for semantically related words than for unrelated words but the difference between LSSG and the two other groups was more constant over time for semantically related words. Extra-list errors variable was positively correlated with three PANSS measures (r=.25-.47). Also, the extra-list errors scores were correlated with the Magical Ideation Scale (r=.34-.39). Memory scores (global explicit, unrelated, related) were significantly and positively correlated with independent living skills (r=.26-.55) and the extra-list errors were negatively correlated with both social support and independent living skills (r=-.29 and r=-.46, respectively). All groups showed a reduction in extraneous false recognition errors/intrusions (FRIs) over time with the HSIG showing the greater change. HSIG and HSDG patients committed slightly more FRIs in recall tasks (extraneous information) than LSSG patients.

CONCLUSION

Memory performance is better in patients presenting with less severe symptomatology. The extent to which FRIs reduce over time in patients with schizophrenia is a novel finding.

Distinguishing between Vascular Dementia and Alzheimer's Disease by Means of the WAIS: A Meta-analysis

This study was intended to, meta-analytically, review whether the subtests of the Wechsler Adult Intelligence Scale are useful in differentiating between vascular dementia and Alzheimer's disease. We expected the Alzheimer's disease group to outperform the vascular dementia group on those subtests that require executive functions, whereas inferior performance of the Alzheimer's disease patients was expected on memory tests. Two steps in the analysis were undertaken in an attempt to clarify this issue. The first step consisted of including all studies examining Wechsler Adult Intelligence Scale subtest performance in vascular dementia and Alzheimer's disease patients. Secondly, a subcortical vascular dementia subgroup was distinguished and performance of this subgroup was compared to that of the Alzheimer's disease group.Overall, the analyses showed that both the vascular dementia and, more strongly, the subcortical vascular dementia group revealed decreased executive functions on several subtests compared to the Alzheimer's disease group. The Alzheimer's disease group showed inferior performance on a single semantic memory test only compared to both the vascular dementia and the subcortical vascular dementia groups. These results indicate that several subtests of the Wechsler Adult Intelligence Scale can differentiate between these two clinical groups, and that most of these tests reveal more impaired performance in the vascular dementia group.

Patterns and clinical correlates of neuropsychologic deficits in patients with schizophrenia

BACKGROUND/PURPOSE

Neuropsychologic deficits are prevalent among schizophrenic patients and are closely associated with pathogenesis and outcome. The pattern, extent, severity and contributing factors to such deficits remain to be examined in Taiwanese schizophrenic patients.

METHODS

A total of 122 schizophrenic patients and 94 healthy subjects for comparison were assessed by a comprehensive neuropsychologic test battery covering the eight cognitive domains of verbal ability, visual spatial ability, abstraction/execution, verbal memory, visual memory, perceptual/motor ability, mental control and attention. The relationships among cognitive deficits, demographic characteristics, clinical historical variables and clinical symptoms were further explored by multivariate regression analysis.

RESULTS

A pattern of selective deficits superimposed on a generalized deficit was found for schizophrenic patients as a group. The mean overall deficit was 1.93 standard deviations below the control mean, and abstraction/execution, verbal memory, visual memory and attention were relatively impaired among the eight cognitive domains. However, there was also marked heterogeneity in individual performances in that 24.2%, 46.2% and 29.5% of patients performed at within normal range, moderately impaired and severely impaired levels, respectively. Duration of illness substantially affected the profile and severity of the deficits, suggesting a progressive deteriorating course in neuropsychological performance. The major predictors of cognitive deficits were number of formal years of education achieved and concurrent severity of disorganization symptoms.

CONCLUSION

In a large sample of schizophrenic patients who underwent comprehensive neuropsychologic evaluation, the current results confirmed that cognitive deficits were prevalent but not a universal feature within schizophrenia. The selective impairment pattern also confirmed that such deficits were mainly in frontal and frontotemporal related functions. Despite evidence suggesting that disease chronicity entailed a decline in selective cognitive domains, the trajectory of the neuropsychologic deficits remains to be examined by further longitudinal studies.

On feeling in control: A biological theory for individual differences in control perception

This review aims to create a cross-disciplinary framework for understanding the perception of control. Although, the personality trait locus of control, the most common measure of control perception, has traditionally been regarded as a product of social learning, it may have biological antecedents as well. It is suggested that control perception follows from the brain's capacity for self regulation, leading to flexible and goal directed behaviours. To this account, a model is presented which spans several levels of analyses. On a behavioural level, control perception may be a corollary of emotion regulation, executive functions, and social cognition. On a neural level, these self-regulatory functions are substantiated in part by the dorsolateral and ventral prefrontal cortex and the anterior cingulate cortex. In addition, a possible role of subcortical-cortical dopamine pathways underlying control perception is discussed.

Shared cognitive processes underlying performance on the Wisconsin Card Sorting Test and the Stroop Test in patients with schizophrenia: a measurement artifact?

We explored the hypothesis that, while sensitive to different aspects of executive functioning in patients with schizophrenia, the Wisconsin Card Sorting Test (WCST) and the Stroop Test also measure the same construct, namely, inhibitory control. Specifically, our goal was to confirm and extend previous findings [A. Rossi, E. Daneluzzo, P. Mattei, M. Bustini, M. Cassachia, P. Stratta, Wisconsin Card Sorting Test and Stroop performance in schizophrenia: a shared construct, Neurosci. Lett. 226 (1997) 87-90] by demonstrating the independence of this construct from other abilities necessary to successfully perform the tasks. More importantly, we sought to improve on this previous study by eliminating the influence of the variance of speed of responding. We examined 55 patients with schizophrenia and initially found that performance on the Stroop Color-Word condition could, indeed, be predicted only by the percentage of perseverative errors on the WCST, and not variables reflective of other cognitive skills, thus replicating and extending previous findings. Once we removed the influence of speed of responding from our measure, however, thus isolating the inhibitory process, this finding disappeared. Therefore, our findings highlight the importance of isolating the individual components of interest from complex measures before drawing conclusions regarding the cognitive processes underlying particular test performance.

Impairment of event schema in patients with schizophrenia: examination of script for shopping at supermarket

The purpose of this study was to examine event schema, the conceptualization of past experience based on script theory, in Japanese patients with schizophrenia. Subjects comprised 25 patients meeting DSM-IV criteria for schizophrenia and 31 normal individuals who gave informed consent. This experiment used three script tasks measuring free recall, frequency judgment, and sequencing of events encountered when shopping at a supermarket. Patients with schizophrenia performed significantly worse than did control subjects on all tasks. In particular, patients committed more errors when judging the events that "occasionally happen" in the frequency judgment task. On the other hand, these patients judged "seldom occurring events" relatively well. Patients with schizophrenia made more errors than normal people in the free recall task. Specifically, patients made more intrusion errors and failed to close scripts. There was a negative correlation between scores the Scale for the Assessment of Positive Symptoms and performance on the free recall task. The results of the present study suggest that event schemas (semantic structure) in patients with schizophrenia are impaired which may be associated with positive symptoms and frontal lobe dysfunction.

Trail making test errors and executive function in schizophrenia and depression

The Trail Making Test (TMT) frequently is used as a measure of executive cognitive function. However, traditional use of test completion time as the primary outcome score does not give the more detailed information on cognitive processes that analysis of test-taking errors may provide. The present study compared TMT performance of three groups: patients with schizophrenia, patients with major depression, and healthy control participants (n = 30 for each group). Three operationally defined error types were examined: (a) tracking, (b) perseverative, and (c) proximity. Although both patient groups were slower than the healthy control group, only the schizophrenia group made significantly more errors, particularly tracking errors, suggesting a greater degree of cognitive disorganization. Within-group analysis of a larger group of schizophrenia patients (n = 84) revealed that TMT time was most strongly associated with the Withdrawal-Retardation factor of the Brief Psychiatric Rating scale. In contrast, TMT errors were most strongly associated with the Conceptual Disorganization factor. Comparisons of TMT scores and other cognitive tests showed moderate to high associations with tests of working memory, psychomotor speed, and executive function. Stepwise regression analysis revealed an independent association between Digit Cancellation and Part B Time, indicating a unique contribution of visuomotor scanning to performance. In contrast, Part B errors were uniquely associated with the Verbal Series Attention Test and the Token Test, tests of mental tracking and executive-mediated working memory, respectively. These findings demonstrate the utility of TMT error analysis in revealing cognitive deficits not traditionally captured using completion time as the sole outcome variable.

Spatial working memory and planning ability: contrasts between schizophrenia and bipolar I disorder

Working memory may be conceptualized as a multi-component system involving the active maintenance and manipulation of stored information in the service of planning/guiding behaviour. Impaired spatial working memory is a robust finding in schizophrenia patients which has been related to an impairment in frontostriatal connectivity. The purpose of this study was to examine the specificity of this impairment by comparing the mnemonic and executive aspects of working memory performance in schizophrenia and bipolar disorder with psychotic features, focusing particularly on the functional dynamics between task components. Twenty-four patients with schizophrenia, 14 patients with bipolar I disorder (manic phase) and 33 healthy control subjects were assessed using the Cambridge Neuropsychological Test Automated Battery (CANTAB): including the spatial working memory (between search errors and strategy scores) spatial span (storage capacity) and spatial planning (Stockings of Cambridge: accuracy and latency) tasks. Both patient groups were impaired on the spatial span task, which requires the maintenance and retrieval of stored information. In contrast, only schizophrenia patients showed a significant deficit in between search errors, which requires both maintenance and manipulation of information in working memory. That is, they exhibited both a mnemonic and an executive dysfunction. Spatial span was particularly important to accurate planning ability in bipolar patients. In contrast, in patients with schizophrenia poor spatial working memory was a significant predictor of planning impairments, consistent with failures in goal selection, evaluation and/or execution. Furthermore, initial planning time was positively correlated with the latency to complete a planning sequence. This pattern of slow cognitive processing in schizophrenia patients only, resembled that reported previously in patients with basal ganglia disorders. These findings are discussed in terms of a possible common disturbance in fronto-parietal circuitry in the two disorders together with a specific disturbance of fronto-striatal circuitry in schizophrenia, that is not present in bipolar disorder.

Evidence that specific executive functions predict symptom variance among schizophrenia patients with a predominantly negative symptom profile

INTRODUCTION

Although deficits in executive functioning in schizophrenia have been consistently reported, their precise relationship to symptomatology remains unclear. Recent approaches to executive functioning in nonschizophrenia studies have aimed to "fractionate" the individual cognitive processes involved. In this study, we hypothesised that if these processes are fractionable, then particular symptom syndromes may be selectively related to executive deficits. In particular, it was hoped that this approach could clarify whether negative and positive symptoms of schizophrenia are differentially related to particular aspects of executive/attentional functions.

METHODS

A total of 32 patients with schizophrenia and 16 matched controls were assessed on a series of tasks designed to tap the theoretically derived executive functions of Inhibition, Shifting set, Working memory, and Sustained attention.

RESULTS

Negative symptoms were significantly predicted by performance on an "Inhibition" task (Stroop), and not by performance on any other task. Furthermore, for a subgroup of patients with predominantly negative symptoms variance in positive symptoms was only significantly predicted by performance on a set-shifting task (Visual Elevator), and not by performance on other tasks, including inhibition.

CONCLUSIONS

Our results support the contention that negative symptoms can, at least partly, be conceived of as cognitive behaviours expressing specific executive deficits. Specifically, we discuss the possibility that negative symptoms may, in part, express a failure in response monitoring. We further suggest that the disordered metacognition resulting in positive symptoms may be mediated by cognitive flexibility in patients with a predominantly negative symptom profile.

The dual origin hypothesis: An evolutionary brain-behavior framework for analyzing psychiatric disorders

According to the dual origin hypothesis, the cerebral cortex of higher mammals evolved from two primordial brain structures, the amygdala and hippocampal formation. This developmental process defines the orderly principles of cortical connectivity and gives rise to functionally distinct ventral and dorsal systems within the cerebrum. This paper reviews the basic features of the dual origin theory. This model is then applied to understanding symptom production in a number of psychiatric illnesses, with particular reference to recent structural and functional imaging studies. In this paper I propose that psychiatric symptoms can be conceptualized as arising from abnormal processing within dorsal (time-space-motility) or ventral (meaning-motivation) systems, or from a disturbance in the functional interaction/balance between them. Within this framework, one can identify symptom-specific correlations that cross-traditional diagnostic boundaries, as well as potential mechanisms that may explain biologically valid diagnostic entities. Integrating evolutionary, connectional and functional bases across multiple species, the dual origin hypothesis offers a powerful neural systems model to help organize our understanding of psychiatric illness, therein suggesting novel approaches to diagnosis, prevention and treatment.

Does negative symptom change relate to neurocognitive change in schizophrenia? Implications for targeted treatments

Negative symptoms and cognitive dysfunction are among the most challenging obstacles in the treatment of schizophrenia. It is unknown to what extent they are overlapping or independent disease processes. In the search for targeted treatments of negative symptoms and cognitive impairments, it is imperative to determine their longitudinal relationship. 267 stable outpatients with schizophrenia in a work and cognitive rehabilitation program were evaluated using symptom measures and a comprehensive neuropsychological test battery at baseline and at the conclusion of rehabilitation, 6 months later. Baseline negative symptom, neuropsychological variables and change scores from intake to follow-up on these variables were correlated. These analyses were repeated with a subsample (n = 161) who had clinically significant negative symptoms at baseline. ANCOVA's were performed to compare patients whose negative symptoms improved by 5 points or more (n = 69) with those whose negative symptoms got worse by 5 points or more (n = 26) on their neurocognitive performance at follow-up. Intake negative symptoms were significantly associated with theory of mind and visuomotor processing. Results failed to support a lawful relationship between change in negative symptoms and neurocognition. These findings suggest that negative symptoms and neurocognition should be viewed as relatively independent targets for intervention.

Relationship of the Wender Utah Rating Scale to objective measures of attention

The Wender Utah Rating Scale (WURS) is a 25-item self-report questionnaire for the retrospective assessment of childhood attention-deficit hyperactivity disorder (ADHD) symptoms; high scores indicate greater symptoms. The current study used 35 male Veterans Affairs outpatients to determine if WURS scores were associated with objective measures of current attentional functioning, including the Trail Making Test, Gordon Diagnostic System, Wechsler Adult Intelligence Scale-Revised digit span and digit symbol subtests, and Wechsler Memory Scale-Revised mental control subtest. Participants included both adults diagnosed with ADHD (n = 14) and non-ADHD adults (n = 21). After Bonferroni correction, Pearson product moment correlation coefficients revealed that greater symptoms on the WURS were associated with poorer digit symbol performance (r = -0.69, P < .05). To determine which indices best predicted WURS scores, scores on attention tests and demographic variables were entered into a stepwise multiple regression analysis. Digit symbol performance was the only significant predictor of WURS scores (R(2) = 0.59, P < .01). Thus, poor performance on a sensitive, but nonspecific, measure of attention with executive function, response speed, and visuomotor coordination components was related to greater self-report of childhood ADHD symptoms.

Dysfunction of the anterior hippocampus: the cause of fundamental schizophrenic symptoms?

Recent evidence suggests there is an association between schizophrenia and dysfunction of the anterior hippocampus. Accordingly, this paper endeavors to show how the fundamental schizophrenic symptoms described by Bleuler might arise from deficiencies in normal hippocampal function. This effort is based on the idea that the hippocampus normally constructs a composite picture or worldview of the environment when conditions are novel or uncertain. Then when conditions become familiar, it influences emotion and behavior to be consistent with that worldview. The anterior hippocampus maintains the emotional component of a worldview through its interaction with the amygdala and hypothalamus, and supports executive frontal lobe activity by way of its output to the nucleus accumbens. From this perspective, the split between affect and cognition in schizophrenia is attributed to a failure of the anterior hippocampus to enforce the emotional component of a worldview allowing emotions to diverge from the cognitive component. The splitting of associations is traced to a failure of anterior hippocampal output to support frontal lobe control over the flow of associations. And a split from reality is seen to arise from a combination of these two failures. The individual ceases to interact with the world because the lack of executive control makes such interaction difficult. Fear and fantasies come to dominate experience because emotions are not adequately controlled.

Neuropsychological correlates of an attention-related negative component elicited in an auditory oddball paradigm in schizophrenia

An attention-related, negative component can be detected between the N100 peak and 200 ms after stimulus by subtracting event-related potentials (ERPs) elicited to background tones when subjects ignore tones, from ERPs elicited to background tones when subjects attend to tones to detect target tones in an oddball paradigm. To clarify the cognitive significance of this component in schizophrenia, we examined the correlations of 24 patients between the amplitude and latency of the negative component and results obtained using neuropsychological measurement methods, including the Wisconsin Card Sorting Test, the Trail Making Test, the Verbal Fluency Test and some subtests from the Wechsler Memory Scale. The latency prolongation of the negative component correlated positively with the difference in performance time between parts A and B of the Trail Making Test, which estimates set shift, a frontal-lobe executive function, but not with any other neuropsychological measurements, while the amplitude showed no such correlation. These results suggest that the latency prolongation of the attention-related, negative component induced in an auditory oddball paradigm may serve as an index for frontal dysfunction in schizophrenia.

Cognitive and clinical moderators of recognition memory in schizophrenia: a meta-analysis

Recognition memory performance in schizophrenia has been shown to vary greatly across studies. To identify the conditions under which recognition memory is significantly impaired, we used a meta-analytic strategy to quantify the moderating effects of several cognitive and clinical variables. Eighty-four studies (from 1965 to July 2003) provided recognition memory data for both a schizophrenia and control group. The overall group comparison for recognition memory yielded a significant mean weighted effect size of d=0.76. Material specificity was the most significant cognitive variable found, with patients exhibiting greater impairment for figural than verbal recognition. A yes-no recognition format and auditory encoding also led to significantly greater effect sizes for recognition memory relative to forced-choice recognition tests and visual encoding, respectively. Furthermore, the effect size for recognition memory as measured by false alarm was smaller than the effect size as measured by hit rate or by d-prime and its related measures. Among clinical variables that were associated with higher effect sizes, chronicity was the most significant, but different trends linking poor performance to negative symptoms and general symptomatology were also observed. Thus, a recognition memory deficit moderated by both cognitive and clinical variables is clearly present in schizophrenia.

Disorganization of semantic memory underlies alogia in schizophrenia: an analysis of verbal fluency performance in Japanese subjects

Patients with schizophrenia exhibit impaired semantic memory as well as deficits in a wide range of language-related functions, such as verbal fluency, comprehension and production of complex sentences. Since language and memory disturbances may underlie some of the psychotic symptoms of schizophrenia, the present study investigated the specific association between alogia (i.e. poverty of speech, poverty of content of speech, blocking, and increased latency of response) and semantic memory organization using the category fluency task (CFT) as a measure of verbal fluency. Thirty-eight patients with schizophrenia and an equal number of normal controls entered the study. Semantic structure was derived from multidimensional scaling analysis using sequential word outputs from the CFT. Patients with schizophrenia revealed disorganized semantic structure (e.g. irregular association of category members) compared with controls, consistent with previous reports. The patients were then divided into two groups, i.e. alogia- and non-alogia subjects, based on the Alogia scores from the Scale for the Assessment of Negative Symptoms (SANS). The symptom-based analysis showed that the semantic structure for the alogia group (Alogia score < or =2) was more disorganized than that for the non-alogia group (Alogia score <1) although the number of words produced did not differ between the two groups. The results of cluster analysis revealed the presence of bizarre coherence specifically in the alogia group. These results indicate that semantic memory disorganization may contribute to the symptom of alogia in schizophrenia. In addition, this is one of the few studies that examined verbal fluency in Japanese patients with schizophrenia and suggest that the language abnormalities in schizophrenia are universal.

Evidence for unaltered brain electrical topography during prefrontal response control in cycloid psychoses

OBJECTIVE

Prefrontal structures such as the anterior cingulate cortex (ACC) play a decisive role in processes of action monitoring and response control, functions often impaired in schizophrenia. Patients with cycloid psychoses exhibit some characteristic neurophysiological features not indicative of the cerebral hypofrontality observed in schizophrenia. This study aimed at examining if cycloid psychoses-unlike schizophrenias-involve a normal brain-electrical topography during a task demanding prefrontal response control.

METHODS

Thirty-seven patients with cycloid psychoses and 37 healthy controls were investigated electrophysiologically while performing a Continuous Performance Test (CPT). Topographical analyses were conducted to individually quantify the Nogo-anteriorisation (NGA) as a neurophysiological index of prefrontal response control.

RESULTS

The patients exhibited an unaltered topography with a mean NGA not significantly different from the controls. They did, however, differ from the control group regarding their Global Field Power (GFP), with a significantly reduced GFP (p<0.001) and decreased latencies (p<0.01) during Nogo trials. On a behavioral level, patients exhibited prolonged reaction times and an increased rate of omission errors.

CONCLUSIONS

The investigated patients showed an activation of specific (presumably frontal) brain areas during Nogo trials, resulting in a frontalisation of the brain-electrical field comparable to the control group. However, the strength of this activation was apparently reduced. The patients' unaltered topographical pattern contrasts with previous findings in schizophrenic patients and supports the hypothesis that cycloid psychoses entail less severe prefrontal deficits than schizophrenias, which might be an indication of different biological backgrounds for both groups of endogenous psychoses.

GABA Targets for the Treatment of Cognitive Dysfunction in Schizophrenia

Cognitive deficits, including impairments in working memory that have been linked to the prefrontal cortex, are among the most debilitating and difficult to treat features of schizophrenia. Consequently, the identification of potential targets informed by the pathophysiology of the illness is needed to develop novel pharmacological approaches for ameliorating these deficits. Postmortem studies of the prefrontal cortex in schizophrenia subjects have revealed disturbances restricted to a subpopulation of inhibitory neurons that includes chandelier neurons, whose axon terminals synapse on the axon initial segment of pyramidal neurons. Chandelier neurons play an important role in synchronizing pyramidal neuron activity and appear to be a critical component of the prefrontal cortical circuitry that subserves working memory function. Therefore, in this paper we review evidence suggesting that drugs which selectively enhance chandelier neuron-mediated inhibition of prefrontal pyramidal neurons may improve working memory dysfunction in schizophrenia. Potential novel targets for such agents include GABA(A) receptors that contain the α(2) subunit. In addition, we discuss potential complementary mechanisms for enhancing inhibitory input to pyramidal cell bodies, including drugs with activity at the CB1 receptor of the endocannabinoid system. The development of pathophysiologically-based treatments that selectively remediate disturbances in specific neural circuits underlying working memory may provide an effective approach to improving cognitive deficits in schizophrenia.